This invention covers an enhanced method for draining thermal oil at a thermal solar plant in which the oil is extracted from a loop in the system, either for processing this oil or for carrying out maintenance operations on the loop. This method consists of a set of stages in which the relevant loop of the thermal solar plant is drained, cooled and refilled. The invention extends to an auxiliary drainage installation designed to carry out this method. This auxiliary unit is specifically a transportable installation.
Thermal solar plants normally comprise a set of mirrors reflecting the sun's radiation and a collection tube on which the radiation reflected by these mirrors is concentrated. A thermal fluid circulates through this tube which gradually heats up as it travels along the circuit through which it has to go.
Thermal solar installations comprise a main conduit of thermal oil in which the means for using this energy are located, as well as the pumping systems or heat exchangers. A set of branch circuits or loops extend from this main conduit, these normally being isolated from the main conduit by means of valves. Hence, any operation which has to be performed on this loop will not prevent the rest of the installation from working.
Thermal fluids involve a high environmental risk through toxicity, and also, at high temperatures, entail a great risk of inflammation or explosion if they come into contact with oxygen. At atmospheric pressure this temperature stands at about 113° C., that is, a temperature under that of the oil in the installation. Working with this type of fluid thus proves extremely dangerous when they are directly withdrawn from the installations. Apart from this, given that the solidification temperature of these oils is very high, around 12° C., they have to be extracted and stored at suitable temperatures, of from 50° C. to 80° C., at which the risk of explosion or inflammation is non-existent and which at the same time allow this to be handled in liquid state.
One subject of this invention is therefore to propose a method for extracting thermal oil from one or more loops in a thermal solar installation, as well as for feeding this back into the installation, which in different stages includes filling auxiliary conduits used for transporting the oil and reducing its temperature to an appropriate level, and later reinserting the oil into the installation and emptying the auxiliary conduits. The capacity of the number of loops in which the drainage operation can be carried out simultaneously will depend on the capacity for storing the thermal oil taken out.
As a second subject of this invention, this also proposes an installation for carrying out the method defined in the claims, which includes a vehicle fitted with pumping and suction means, an oil cooling device fitted with heat exchangers and means for dissipating the heat, auxiliary conduits and a set of manually or automatically operated valves.